Clinical Scorecard: Interim Results of a Phase II Trial on 68Ga-PSMA-PET Imaging and Transponder-Guided Salvage Radiotherapy Targeting the Prostate Bed for Biochemical Recurrence Post-Prostatectomy

At a Glance

Key Highlights

• 68Ga-PSMA-PET improves detection of local recurrence and influences treatment strategy, reducing unnecessary androgen deprivation therapy (ADT).
• Transponder-guided SRT allows real-time target tracking, potentially reducing rectal toxicity and improving treatment accuracy.
• Interim 3-year results focus on freedom from biochemical relapse, toxicity profiles, and patient-reported quality of life outcomes.

Guideline-Based Recommendations

Diagnosis

• Use 68Ga-PSMA-PET combined with standard contrast-enhanced CT for staging in biochemical recurrence with PSA 0.1–2.5 ng/mL.
• Exclude patients with metastatic disease outside the prostate bed before salvage therapy.

Management

• Offer salvage radiotherapy to the prostate bed at earliest biochemical recurrence, ideally when PSA <0.5 ng/mL.
• Deliver 70 Gy in 35 fractions for 68Ga-PSMA-PET negative patients or 74 Gy in 37 fractions if positive in prostate bed only.
• Use implantable electromagnetic transponders for real-time target tracking in suitable patients to optimize radiotherapy delivery.
• Avoid androgen deprivation therapy in patients with local recurrence only to reduce overtreatment and preserve quality of life.

Monitoring & Follow-up

• Follow-up with PSA testing, clinical evaluation, toxicity assessment, and quality of life questionnaires at 6 weeks post-SRT, quarterly for 2 years, then every 6 months.
• Define biochemical relapse as PSA increase >0.2 ng/mL from post-radiotherapy nadir with confirmatory reading.

Risks

• Potential rectal toxicity and undertreatment due to prostate bed movement during radiotherapy without real-time tracking.
• ADT may improve survival but is associated with reduced quality of life and increased mortality from other causes.

Patient & Prescribing Data

Men with biochemical recurrence of prostate cancer post-radical prostatectomy, PSA 0.1–2.5 ng/mL, no distant metastases.

Transponder-guided SRT targeting the prostate bed alone without ADT is feasible and may reduce overtreatment; 68Ga-PSMA-PET imaging guides patient selection and treatment planning.

Clinical Best Practices

• Screen patients with rising PSA post-prostatectomy using 68Ga-PSMA-PET combined with CT to accurately stage disease.
• Implement transponder implantation for real-time target tracking in eligible patients to minimize radiation exposure to adjacent organs and improve treatment precision.
• Tailor radiotherapy dose based on PET findings: standard dose for negative PET and escalated dose for PET-positive prostate bed lesions.
• Avoid ADT in patients with isolated local recurrence to preserve quality of life unless metastatic disease is detected.
• Conduct regular and structured follow-up including PSA monitoring and patient-reported outcomes to assess treatment efficacy and toxicity.

References

• Prostate cancer recurrence and salvage radiotherapy guidelines
• 68Ga-PSMA-PET imaging in prostate cancer
• Calypso® transponder system for prostate bed radiotherapy